I do need XP to connect to the internet for a number of the programs I run on it (Outlook, Quicken, etc). I upgraded the computer's RAM from 2GB to 4GB (my max) over the weekend and moved some large photo files from the XP to my external drive to free up about 10GB of space on the vm, and both the host and vm now appear to be running much better. So I am going to give it another week or so before I consider doing anything else. Hopefully I won't have to. It appears to have been just a problem of insufficient resources, not corruption of the XP.
Thanks for your help.